When Major League Soccer and the USL announced a groundbreaking, multi-year partnership in early 2013 designed to enhance the development of professional players in North America, the ramifications for the two leagues, and the sport as a whole, were yet to be fully understood.

More than two years later, the partnership between the two leagues cannot be viewed as anything other than a resounding success. With the 2015 season seeing full integration between the two leagues - with MLS clubs either partnering with current USL clubs or entering their own side in the USL - both leagues have seen positives on and off the field.

2014 saw the addition of the LA Galaxy II to the USL, the first team in league history to be owned and operated by an MLS club. In all, the Galaxy sent 14 players on loan from their first team to Los Dos, including six Homegrown Players, who recorded more than 12,000 minutes of action and 38 goals in the regular season as the club finished third in the USL standings.

The Galaxy II’s success prompted seven additional MLS clubs to enter their own sides for 2015, with teams such as the Timbers 2, Sounders 2 and Real Monarchs all eager to emulate the success Los Dos found on the field. For 2016, the Philadelphia Union have announced a club in Pennsylvania's Lehigh Valley, and the Houston Dynamo are scheduled to partner with newly-announced Rio Grande Valley FC, which is constructing its own 10,000-seat soccer-specific stadium.

"The addition of seven MLS teams is a testament to the success that the Galaxy had in terms of getting some of their players really meaningful game time in a proper professional league," USL President Jake Edwards told ESPN.com. "Some of those guys have even got back in the first team and played in MLS Cup. For them it was a huge success."

The USL has also seen substantial growth in its ranks in independent clubs, with new teams joining in 2015 in Austin, Charlotte, Colorado Springs, Louisville, Saint Louis and Tulsa looking to emulate the success of Sacramento Republic FC, which claimed the league championship in its inaugural season.

Bethlehem Steel FC, FC Cincinnati, Orlando City B, Rio Grande Valley FC and Swope Park Rangers KC have joined the mix for 2016, and a club in Reno, Nevada - owned by Indiana Pacers owner Herb Simon - is set to begin play in 2017.

With a strong business model and outstanding front office leadership, the USL has become the league of choice for investors looking to build a professional club from the ground up in North America.

“We believe our goal of building a strong league that puts an emphasis on regional rivalries and a continued elevation of play through our partnership with MLS, has resonated with the new ownership groups that have joined the league,” Edwards said. “The league has raised its standards on and off the field each season."